NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | CONFORMING TO | NOTES | SEE ALSO | COLOPHON

WPRINTF(3)                Linux Programmer's Manual               WPRINTF(3)

NAME         top

       wprintf, fwprintf, swprintf, vwprintf, vfwprintf, vswprintf - format‐
       ted wide-character output conversion

SYNOPSIS         top

       #include <stdio.h>
       #include <wchar.h>

       int wprintf(const wchar_t *format, ...);
       int fwprintf(FILE *stream, const wchar_t *format, ...);
       int swprintf(wchar_t *wcs, size_t maxlen,
                    const wchar_t *format, ...);

       int vwprintf(const wchar_t *format, va_list args);
       int vfwprintf(FILE *stream, const wchar_t *format, va_list args);
       int vswprintf(wchar_t *wcs, size_t maxlen,
                     const wchar_t *format, va_list args);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       All functions shown above:
           _XOPEN_SOURCE >= 500 || _ISOC99_SOURCE ||
           _POSIX_C_SOURCE >= 200112L;
           or cc -std=c99

DESCRIPTION         top

       The wprintf() family of functions is the wide-character equivalent of
       the printf(3) family of functions.  It performs formatted output of
       wide characters.

       The wprintf() and vwprintf() functions perform wide-character output
       to stdout.  stdout must not be byte oriented; see fwide(3) for more
       information.

       The fwprintf() and vfwprintf() functions perform wide-character
       output to stream.  stream must not be byte oriented; see fwide(3) for
       more information.

       The swprintf() and vswprintf() functions perform wide-character
       output to an array of wide characters.  The programmer must ensure
       that there is room for at least maxlen wide characters at wcs.

       These functions are like the printf(3), vprintf(3), fprintf(3),
       vfprintf(3), sprintf(3), vsprintf(3) functions except for the
       following differences:

       ·      The format string is a wide-character string.

       ·      The output consists of wide characters, not bytes.

       ·      swprintf() and vswprintf() take a maxlen argument, sprintf(3)
              and vsprintf(3) do not.  (snprintf(3) and vsnprintf(3) take a
              maxlen argument, but these functions do not return -1 upon
              buffer overflow on Linux.)

       The treatment of the conversion characters c and s is different:

       c      If no l modifier is present, the int argument is converted to
              a wide character by a call to the btowc(3) function, and the
              resulting wide character is written.  If an l modifier is
              present, the wint_t (wide character) argument is written.

       s      If no l modifier is present: The const char * argument is
              expected to be a pointer to an array of character type
              (pointer to a string) containing a multibyte character
              sequence beginning in the initial shift state.  Characters
              from the array are converted to wide characters (each by a
              call to the mbrtowc(3) function with a conversion state
              starting in the initial state before the first byte).  The
              resulting wide characters are written up to (but not
              including) the terminating null wide character (L'\0').  If a
              precision is specified, no more wide characters than the
              number specified are written.  Note that the precision
              determines the number of wide characters written, not the
              number of bytes or screen positions.  The array must contain a
              terminating null byte ('\0'), unless a precision is given and
              it is so small that the number of converted wide characters
              reaches it before the end of the array is reached.  If an l
              modifier is present: The const wchar_t * argument is expected
              to be a pointer to an array of wide characters.  Wide
              characters from the array are written up to (but not
              including) a terminating null wide character.  If a precision
              is specified, no more than the number specified are written.
              The array must contain a terminating null wide character,
              unless a precision is given and it is smaller than or equal to
              the number of wide characters in the array.

RETURN VALUE         top

       The functions return the number of wide characters written, excluding
       the terminating null wide character in case of the functions
       swprintf() and vswprintf().  They return -1 when an error occurs.

CONFORMING TO         top

       C99.

NOTES         top

       The behavior of wprintf() et al. depends on the LC_CTYPE category of
       the current locale.

       If the format string contains non-ASCII wide characters, the program
       will work correctly only if the LC_CTYPE category of the current
       locale at run time is the same as the LC_CTYPE category of the
       current locale at compile time.  This is because the wchar_t
       representation is platform- and locale-dependent.  (The glibc
       represents wide characters using their Unicode (ISO-10646) code
       point, but other platforms don't do this.  Also, the use of C99
       universal character names of the form \unnnn does not solve this
       problem.)  Therefore, in internationalized programs, the format
       string should consist of ASCII wide characters only, or should be
       constructed at run time in an internationalized way (e.g., using
       gettext(3) or iconv(3), followed by mbstowcs(3)).

SEE ALSO         top

       fprintf(3), fputwc(3), fwide(3), printf(3), snprintf(3)

COLOPHON         top

       This page is part of release 3.72 of the Linux man-pages project.  A
       description of the project, information about reporting bugs, and the
       latest version of this page, can be found at
       http://www.kernel.org/doc/man-pages/.

GNU                              2014-03-19                       WPRINTF(3)